Re: [tor-dev] Pluggable Transports 2.0 Specification, Draft 3

nickm requested that I provide the following information about the PT 2.0 specification draft:

The only section that requires changes to tor is Section 3.3.4, on client per-connection arguments.

Implementing the requirements from this section are discussed in the following trac ticket: https://trac.torproject.org/projects/tor/ticket/21816

Here is the entirety of the proposal text that requires changes to tor, for your convenience:

If there are connection settings present, the authentication type 0x09 (IANA assigned, “JSON Parameter Block”) is used, followed by the serialized per-connection parameter data. The serialization process for the parameters is defined as follows:

● They keys and values are inserted into a map
● This map is serialized JSON to a UTF-8 string.

● The UTF-8 string is converted to a sequence of bytes. (This is trivial for a UTF-8 string.)
● The number of bytes is counted.
● The byte count is encoded as a 4-byte sequence in network byte order (big-endian).
● The encoded count is prepended to the byte sequence.

The following error codes are defined for the response when connection settings are present:

● X’10’ - Connection settings size too large
● X’11’ - Timeout reading connection settings
● X’12’ - Error parsing connection settings
● X’13’ - Connection settings have invalid or missing keys or values

While the byte count is encoded as a 4-byte sequence, which is capable of expressing connection setting sizes up to 4GB, it is not required that the implementation support the maximum possible size. If a size larger than is supported by the implementation is specified, the X’10’ error code can be used. Additionally, an implementation-dependent timeout should included for receiving the connection settings. If this timeout is exceeded, the X’11’ error code can be used. Error code X’12’ is returned if the connection parameters are not properly encoded JSON. Error code X’13’ is used if the connection settings are not correct for the specific transport being used.

Example

\x00\x00\x00\x39{"shared-secret": "rahasia", "secrets-file": "/tmp/blob"}

On Thu, Oct 12, 2017 at 2:38 PM, Brandon Wiley <brandon@xxxxxxxxx> wrote:

Below is a link to the third draft of the Pluggable Transport 2.0 Specification. If you have feedback on this draft, please send me your comments by October 31. Thank you!

Changes in this version:
Expanded acknowledgements section - thanks Yawning!
Removed TransportConn and TransportListener in favor of net.Conn and net.Listener
Modified SOCKS authentication method to use IANA-assigned designator
Added error response codes for per-connection arguments
Many typos fixed - thanks David Fifield!
Clarified some definitions - thanks teor!

Link: https://operatorfoundation.org/PluggableTransportSpecification-v2-Draft3.pdf